不同季节绿茶中茶多酚、咖啡碱和氨基酸含量分析

绿茶我国被誉为"国饮".大量科学研究证实,绿茶中的茶多酚、咖啡碱和氨基酸等具有一定的药理功效.绿茶一年有三季,分别为春茶、夏茶和秋茶,其中春茶和秋茶的口感相似,但是市场价格却相差几十倍,但是其主要成份是否有差异,并未见报导.该研究用国标法和红外光谱法分别对南京地区新鲜的春季茶和秋季绿茶样品中茶多酚、咖啡碱和氨基酸进行分析,两者的实验结果都为春季绿茶中茶多酚、咖啡碱和氨基酸的量高于秋季绿茶.     

Prebiotic oligosaccharides change the concentrations of short-chain fatty acids and the microbial population of mouse bowel

The purpose of this study was to clarify effects of selected oligosaccharides on concentrations of cecal short-chain fatty acids (SCFAs), total large bowel wet weight and wall weight, and cecal microbiota levels in mice. Mice were respectively given gavage of selected fructooligosaccharides (FOS), galactooligosaccharides (GOS), mannanoligosaccharides (MOS), and chitooligosaccharides (COS) [1000 mg/(kg body weight.d)]. Control group was given physiological saline solution. After 14 d treatment, SCFAs and lactate in mice cecum were significantly increased (P<0.05) by intake of oligosaccharides, especially FOS and GOS. Thus, providing these oligosaccharides as ingredients in nutritional formulas may benefit the gastrointestinal tract.     

A comparative study of the effects of a concept mapping enhanced laboratory experience on Turkish high school students’ understanding of acid-base chemistry

The research reported here consists of the introduction of an intervention based on a series of laboratory activities combined with concept mapping. The purpose of this intervention was to enhance student understanding of acid-base chemistry for tenth grade students’ from two classes in a Turkish high school. An additional aim was to enhance student attitude toward chemistry. In the research design, two cohorts of students were compared; those from the intervention group (N = 31) and a second group (N = 28) who were taught in a more traditional manner. Student understanding of acid-base chemistry was evaluated with a pretest/posttest research design using a purpose-designed instrument, the Concept Achievement Test (CAT) consisting of 25 items, 15 multiple choice and ten multiple choice with explanation. Alternative conceptions identified in the pretest were incorporated into the intervention, which thereby sought to move students toward views more in accord with scientific views for the concepts. Statistical tests indicate the instrument is reliable (with an alpha reliability of 0.81) and the analysis of the findings revealed statistically significant differences between the intervention and traditional groups with respect to conceptual understanding. Examination of student explanations and analyses of semi-structured interviews conducted with selected students suggest that the main influence was the laboratory activities. Analysis of the findings in the context of relevant literature that concept mapping in conjunction with laboratory activities is more enjoyable, helps student link concepts, and reduces their alternative conceptions.     

烤烟氨基酸含量变化规律研究

研究了不同生育时期、品种、施肥量、叶位以及烘烤前后烟叶氨基酸含量的变化规律.结果表明,旺长期的氨基酸含量较高,进八成熟期后含量急剧下降,烟叶烘烤后,除胱氨酸、蛋氨酸和赖氨酸的含量降低外,其余14种氨基酸及氨的含量均升高.其中,升幅最大的为脯氨酸,烤后与烤前之比为4.50;相反,降幅最大的是蛋氨酸,烤后与烤前之比为0.34.上二棚叶的氨基酸含量高于或接近腰叶.不同耐肥品种间差异较大的氨基酸是脯氨酸和天门冬氨酸,并且以耐肥性强的品种高于耐肥性弱的品种,氨基酸含量与施肥量正相关,增幅较大的为谷氨酸.天门冬氨酸和脯氨酸.烤烟叶片氨基酸含量变异较大的是脯氨酸、谷氨酸和天门尽氨酸,可作为烟株N素营养状况与品种耐肥性的生理指标.     

直接进样法测定植物油中的脂肪酸

对植物油不经衍生化直接进样对脂肪酸进行测定 ,采用毛细管气相色谱法分析植物油中的脂肪酸成分和含量 ,其灵敏度比 GC(普通填充柱气相色谱法 )提高了 1 0 2～ 1 0 3倍     

Simultaneous detection of seven phenolic acids in Danshen injection using HPLC with ultraviolet detector

A high-performance liquid chromatographic (HPLC) method with ultraviolet (UV) detector had been developed for simultaneous quantification of danshensu, protocatechuie aldehyde, caffeic acid, salvianolic acid D, rosmarinic acid, salvianolic acid B and salvianolic acid A in Danshen injection. According to the UV spectra of these components, three detection wavelengths have been selected as follows: 280 nm for danshensu and protocatechuic aldehyde, 326 nm for caffeic acid, salvianolic acid D and rosmarinic acid, 286 nm for salvianolic acid B and salvianolic acid A. The limit of detection (LOD) was improved to be in the range of 0.008～0.160 μg/ml. Moreover, excellent linear behavior over the investigated concentration range was observed, with R>0.999 for all the analytes.     

强弱酸混合液PH计算新方法

本文应用解析法以质子等衡式为依据,先分别算出强,弱酸的酸度,再用加合公式把它们加合起来,以算出混酸溶液的PH,该法比原有方法简便,适用性广,算出的结果也较准确。     

九州虫草与冬虫夏草、蛹虫草氨基酸成分比较

研究了九州虫草有效部位的氨基酸组成,并与冬虫夏草及蛹虫草进行了比较.测定结果表明所测样品中分别含有16-18种氨基酸,必需氨基酸含量都较丰富,分别占每种样品氨基酸总量的66.93%、34.48%、46.18%、46.62%、38.96%、37.38%.结果表明九州虫草无论是菌丝体还是子座,在氨基酸方面具有较高的营养价值和药用保健价值.     

气相色谱法测定花生油掺伪的方法研究

用气相色谱法测定了花生油和一些常见植物油的脂肪酸组成及其含量,使用添加法在花生油中掺入不同种类、不同浓度的植物油,并进行了相关分析.发现油中脂肪酸组成及其特征组分的变化成线性规律,由此做出工作曲线,可快速定性、定量掺伪油,且掺伪量的最低检出限可达到5%.     

银纳米基比色传感法测定水样中汞离子的方法

基于银纳米粒子在盐诱导下聚集使体系颜色发生改变这一原理,建立一种生物传感方法检测水样中的汞离子.采用柠檬酸还原法合成银纳米粒子并修饰以核酸适配体,汞离子与核酸适配体结合发生变构效应导致银纳米粒子暴露在盐环境中发生聚集,使体系光谱特征峰和颜色发生明显变化.研究体系特定波长吸光度比值与汞离子浓度的变化关系.在最佳优化条件下,该比色法在质量浓度区间为0.2~50 ng/mL呈现良好线性关系,检出限为0.11 ng/mL.将该检测体系应用于汞离子类似物的检测,特异性较好.该方法对水样中汞离子的检测有一定的应用前景.